矿物型润滑油总酸值测定新方法(电位法)探讨

Discussion on a New Method(Potentiometric Titration) for Determining Total Acid Number of Mineral Lubricating Oil

文章利用石油醚、无水乙醇和少量水作为混合溶剂,将矿物型润滑剂完全溶解,再加热至50～55℃且搅拌均匀成均相体系,再以0.05mgKOH/g乙醇溶液作为标准溶液,然后参照GB/T 7304的方法利用电位滴定仪对其进行测定,从而得到润滑油的总酸值。该方法克服了原GB/T 7304中甲苯毒性大、刺激性较强、对分析工作者的身体健康带来一定影响的不利因素。实验表明,用新方法平行数据能满足GB/T 7304重复性要求,新旧两种方法的测定结果经统计检验具有一致性、准确性,新方法的相对标准偏差至少小于2.80%。

The mineral lubricating oil was dissolved completely in the mixed solvent of petroleum ether,anhydrous ethanol and small amount of water.Then the mixed solvent was heated to 50~55 ℃ and stirred to homogeneous phase system.Referring to the GB/T 7304 method,taking 0.05 mgKOH/g ethanol aqueous as standard solution,the total acid number of the mineral oil was determined by means of potentiometric titrator.This method overcomes the negative factors of original GB/T 7304 method such as the high toxicity of toluene,strong irritation and harmful to the health of operators.Experimental results show that the panel data from the new method can meet the repeatability required by GB/T 7304.By statistical testing,the result of the new method（potentiometric titration） is consistent and accurate with the result of the old one,with the relative standard deviation of less than 2.80% at least.